Optical Spectroscopy in the Infrared Range

Beyond intramolecular modes of species present in the electrolyte solution or interacting with an electrode surface, modes caused by adsorptive interaction between the adsorbed species and the electrode surface can be studied (e.g. the silver-halide stretching mode with surface enhanced Raman spectroscopy (SERS) for details. 

Fundamentals, applications and experimental details of both infrared and Raman spectroscopy are treated in numerous textbooks and handbooks [149-157] thus only a few general details of these spectroscopies, which are of particular importance for applications in electrochemistry, are treated here. 

Infrared spectroscopy, as applied in numerous different experimental setups for electrochemical investigations, is at first glance seriously hampered by the fact that most electrolyte systems (including both the solvent and the dissolved supporting electrolyte) tend to absorb infrared radiation strongly. Thus the detection of absorption of radiation of species present in an adsorbate layer or dissolved in this electrolyte solution is difficult. Various approaches have been described to overcome this problem. 

With attenuated total reflection spectroscopy, the light absorption by the electrolyte solution and the cell window is no obstacle. The probe beam enters a crystal transparent for infrared light. It is directed to the outer surface of the crystal, which is coated with a thin layer of the electrode material under investigation. The beam is reflected, but a small part (the evanescent wave) penetrates the surface and thus can probe species located immediately on the electrode surface. The returning beam contains exactly this information. As discussed below (p. 91) in detail, this approach shows also serious limitations. 

The use of a Fourier transform infrared (FTIR) spectrometer has provided a completely different methodological approach to this spectroscopy [160,161]. The central component of any FTIR spectrometer is an interferometer. No dispersive elements are used. Based on the construction, various advantages in comparison 

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Optical Spectroscopy in the Infrared Range /CaF2 prism... 

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